2009©forensic science today1 crime scenes physical evidence- any object that can establish that a...

2009©Forensic Science Today 1

Crime Scenes

Physical Evidence- Any object that can establish that a crime has been

committed or can link a crime and its victim or its perpetrator


Secure the Scene

Why? -to keep others out

-to prevent alteration & destruction

How? –tape off area large enough to contain

all possible evidence (w/in reason)


Responsibilities of First Responder

Obtain medical assistance if necessary

Arrest the perpetrator

Preserve and protect the area

Exclude all unauthorized personnel from the scene


Search the SceneRecord-take notes, photos and sketch (Do not alter the scene!) Points of entry and exit must be noted.Choose a method-systematicGloves

Quadrant search


Photographing the Scene

Scene must be in unaltered condition for photos to be admissible in court.Necessary movement of evidence must be noted in the report but cannot be reintroduced as a “staged” photo.Take overview scenes of entire area and adjacent surroundings.Include points of entry and exit


If a body is present,

photograph the position and location relative to the entire scene.

take close-ups of injuries and weapons.

When appropriate to move the body, take pictures of the surface beneath the body.

Include a ruler as a point of reference to document size.


Sketches

Rough sketch

drawn at the scene

contains an accurate depiction of the dimensions of the scene and shows the location of all object having a bearing on the case

Finished sketch

a precise rendering drawn to scale (CAD- computer aided drafting)


Notes

Detailed description of physical evidence including time of discovery, who discovered it, how it was discovered, and who packaged the evidence, and the disposition of the evidence.

May be the only source of info for refreshing one’s memory on a cold case

Tape recording and video recording is useful.


Chapter 2 The Crime Scene Part II

Objectives:

Describe proper procedures for conducting a systematic search of a crime scene for physical evidence

Describe proper techniques for packaging evidence

Define the concept of Chain of Custody


Goals of the Crime Scene SearchProvides information on the “Corpus Delicti” (“body of the crime”)Provides information on the “Modus Operandi” (“mode of operation” or MO)Links a suspect with a victimLinks a person with a crime sceneDisproves or supports and alibi or witness’s testimonyIdentifies a suspectProvides investigative leadsIdentifies unknown substances


Theories of Crime Scene Searches

Linkage Theory: The case can be solved if investigators can establish

links between physical evidence and the victim, crime scene and/or suspectTransfer Theory:

Based on Locard’s Theory of ExchangeWhenever you leave a location, you leave something

behind (hair, soil from shoes, etc.) and take something with you. (fibers)


Conduct a thorough searchOrganization and experience are critical- chief officer to assign dutiesView scene as a whole initially (look for missing items as well as evidence)Consider the possibility of a primary or secondary crime sceneScene must be guarded at all times until it is released.Scene MUST remain intact unless absolutely necessary. Document any changes. (e.g. removal of evidence, closing a window)


Search Methods (see p. 41)Strip or line search

Useful in large, outdoor areas

Grid method- more thorough version of line search

Spiral method-Danger- evidence may be destroyed if investigators initially walk to the center to begin search

Zone searchUseful in indoor searches

Wheel methodUsed in special situations, not in large areas

Link methodUsed in conjunction with the above


Experience Rules

Good Crime scene investigators “expect the unexpected” and “leave no stone unturned”


Types of Searches


Notetaking

Date/Time of Arrival

Name

Address/Description

Weather Conditions

Log of All Activities


Sketch the Scene

All evidence found

Measurements, 2 from fixed points

Orientation & Direction (North directional marker)

Labels for representing evidence


Measure Each Piece of Evidence

From two fixed points or using triangulation.


Photograph

Overview

Rooms or areas near the scene

Entry/Exit

Physical evidence

Close-ups and perspective


Collection

Separate containers

Gloves

Label outside of container

Seal the container


From the BodyCollect*hair and fiber*clothing*blood sample*bullets*hand swabs from shooting victims for GSR analysis*fingernail scrapings*oral, anal and vaginal swabs in sexual assaults*organ samples for possible testing


Containers – See appendix I pp. 543-555

In order to prevent loss or damage:

*Appropriate size

*Appropriate type

Suitable for most trace evidence


Container Types

Body Fluids –in porous container to avoid formation of mold or mildew

Glass or other breakables –in rigid container

Metal objects –in rigid container

Bloodstained materials should not be stored in air-tight containers


More Container Types

Trace Evidence –in Druggist fold w/ container that allows no leakage

Arson Evidence- in nonporous & unbreakable container


Labeling

On outside of container place…

*Name

*date

*time

*description of evidence

Tamper-proof seal is required


Seal on the container

Cover opening w/ seal

Write on seal

*initials

*date

Maintain proper Chain of Custody


Obtain Standard/Reference Samples

For comparisonExamples may include paint from a suspect vehicle, hairBloodstained evidence must include a buccal swab (swab from the inner portion of cheek of crime-scene participants for DNA comparison)Substrate Control-materials close to areas where evidence has been deposited (Arson cases, bloodstains)


Chain of Custody

Who…

When…

What…

Where…

Why maintain chain of custody?


Maintain Chain of Custody

Transfer of evidence must be recorded

Everyone involved in the collection and transportation of evidence may be requested to testify

To avoid confusion

To retain complete control of evidence at all times


Submit Evidence to Lab

See p. 48 Fig 2-8 for Evidence submission form

Mail is acceptable if packaging is appropriate

Each item packaged separately

Each item assigned an identifying number or letter referenced on form


Release the Scene

Reasonable time

Check walk through

Record

*released to…

*date/time

Warrant


Crime Scene SafetyPPE includes gloves and coverall gowns; surgical masks and protective eyewear is required when handling bodily fluids or attending an autopsy.Avoid contact with biohazards (i.e. blood and bodily fluids)OSHA requires law enforcement agencies to offer Hepatitis B vaccines for employees at no costBe wary of sharp objectsNo smoking, drinking or eating or application of make-up Label evidence contaminated with body fluids as “Caution-Potential AIDS (or Hepatitis) CaseContact authorities when dealing with explosivesClean hands with diluted bleach solution, soap and water. Discard contaminated shoes and clothing.

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Legal Considerations

Searches must conform to the Fourth Amendment

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizure, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.


Warrants

Probable cause

Warrantless searchesConsent given

Evidence in immediate danger of loss

Emergency circumstances exist

Someone being lawfully arrested

2009©forensic science today1 crime scenes physical evidence- any object that can establish that a...

Documents

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necessary movement of